Poynting Vector and Theorem
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Questions and Answers

When electromagnetic waves travel in space, they carry ______.

energy

Energy density is always associated with electric fields and ______.

magnetic fields

The concept of the Poynting vector relates to the flow of ______ in electromagnetic fields.

energy

Electromagnetic waves consist of oscillating electric and ______ fields.

<p>magnetic</p> Signup and view all the answers

The Poynting theorem helps in understanding the conservation of ______ in electromagnetic systems.

<p>energy</p> Signup and view all the answers

The ______ vector is a key concept in electromagnetics.

<p>Poynting</p> Signup and view all the answers

Poynting's theorem relates to the conservation of ______ in electromagnetic fields.

<p>energy</p> Signup and view all the answers

The complex form of the Poynting vector provides a more ______ representation of electromagnetic energy.

<p>detailed</p> Signup and view all the answers

This content is part of the curriculum for ______ physics.

<p>medical</p> Signup and view all the answers

The lectures discussed are from the ______ year of the program.

<p>second</p> Signup and view all the answers

The Poynting vector is represented mathematically as the ______.

<p>instantaneous energy flux density</p> Signup and view all the answers

The direction of the Poynting vector is perpendicular to the plane containing ______ and H.

<p>E</p> Signup and view all the answers

The Poynting vector is also known as ______.

<p>instantaneous energy flux density</p> Signup and view all the answers

In electromagnetic theory, the Poynting vector represents the flow of ______.

<p>energy</p> Signup and view all the answers

The Poynting vector's direction is based on the cross product of ______ and H.

<p>E</p> Signup and view all the answers

The rate of energy transfer is represented by the vector ______.

<p>P</p> Signup and view all the answers

The vectors ______ and H are perpendicular to the rate of energy transfer.

<p>E</p> Signup and view all the answers

The unit of the rate of energy transfer is ______ per unit area.

<p>W/m²</p> Signup and view all the answers

The rate of energy transfer vector P is perpendicular to both the electric field E and the magnetic field ______.

<p>H</p> Signup and view all the answers

Energy transfer occurs at a rate denoted by the vector ______.

<p>P</p> Signup and view all the answers

Poynting theorem states that the net power flowing out of a given volume V is equal to the time rate of decrease of stored electromagnetic ______ in that volume.

<p>energy</p> Signup and view all the answers

The net power flowing out of a volume is decreased by the conduction ______.

<p>losses</p> Signup and view all the answers

The theorem connects net power flow with the rate of energy ______ in a specified volume.

<p>decrease</p> Signup and view all the answers

______ theorem applies to the electromagnetic energy within a certain volume.

<p>Poynting</p> Signup and view all the answers

In Poynting theorem, the term 'net power' refers to the total ______ of power leaving a volume.

<p>flow</p> Signup and view all the answers

The rate of energy travelled through per unit area is called the ______ vector.

<p>Poynting</p> Signup and view all the answers

The amount of energy flowing through per unit area in the perpendicular direction is part of the definition of ______.

<p>Poynting vector</p> Signup and view all the answers

Energy flows through per unit area in the ______ direction to the incident energy per unit time.

<p>perpendicular</p> Signup and view all the answers

The flow of energy is measured in terms of energy per unit area per unit ______.

<p>time</p> Signup and view all the answers

The ______ vector is an important concept in the study of electromagnetic theory.

<p>Poynting</p> Signup and view all the answers

Flashcards

Electromagnetic Wave

A disturbance that propagates through space carrying both electric and magnetic fields.

Energy Density

The amount of energy stored per unit volume in a physical system.

Poynting Vector

A vector quantity representing the direction and magnitude of the energy flow in an electromagnetic wave.

Poynting Theorem

A mathematical equation that relates the energy flow in an electromagnetic wave to the rate of change of the energy density.

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Energy Associated with E & B Fields

Electromagnetic waves store energy in both their electric (E) and magnetic (B) fields.

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Net Power Flow

The total power leaving a specific volume, taking into account both incoming and outgoing power.

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Stored Electromagnetic Energy

Energy stored within electric and magnetic fields within a specific volume.

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Time Rate of Decrease

How quickly the stored electromagnetic energy within a volume is decreasing.

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Conduction Losses

Energy loss due to the resistance of materials within the volume, turning electromagnetic energy into heat.

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Complex Poynting Vector

A complex-valued version of the Poynting vector that takes into account both the real and imaginary parts of the electromagnetic fields. It is particularly useful for analyzing waves in complex media.

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Electromagnetism for Medical Physics

The study of electromagnetic phenomena and their applications in medical physics, including imaging, therapy, and diagnostics.

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Complex form of Poynting Vector

A way to represent the Poynting vector using complex numbers, allowing for the inclusion of both amplitude and phase information of the electromagnetic fields. It is particularly useful for analyzing electromagnetic waves in complex media.

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Poynting Vector Equation

Mathematically, the Poynting vector (S) is expressed as the cross product of the electric field (E) and the magnetic field (H). S = E x H.

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Energy Flow Rate

The amount of energy passing through a given area in a specific time interval.

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Direction of Energy Flow

Poynting Vector's direction indicates the path along which energy is travelling.

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Poynting Vector Direction

The Poynting vector points in the direction of energy flow, which is perpendicular to both the electric field (E) and the magnetic field (H).

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Instantaneous Energy Flux Density

The Poynting vector describes the rate of energy flow per unit area at a particular point in time. It's the instantaneous energy flux density.

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Perpendicular Area

The area considered for energy flow is perpendicular to the path of the energy.

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Units of Poynting Vector

The Poynting Vector is measured in units of Watts per square meter (W/m²).

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Poynting Vector Application

The Poynting vector is crucial for understanding the transfer of electromagnetic energy in various situations, such as electromagnetic waves, power transmission lines, and antennas.

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Energy Transfer Rate

The rate at which energy is transferred per unit area, represented by the Poynting Vector.

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Direction of Energy Transfer

The direction of energy transfer in an electromagnetic field is given by the direction of the Poynting Vector.

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Relationship between Poynting Vector, Electric Field, and Magnetic Field

The Poynting Vector (P) is perpendicular to both the electric field (E) and magnetic field (H) in an electromagnetic field.

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Study Notes

Poynting Vector and Theorem

  • Electromagnetic waves carry energy and energy density is associated with electric and magnetic fields.
  • Poynting vector represents the rate of energy flow per unit area.
  • Mathematically, the Poynting vector (P) is represented as P = E x H / μ.
  • The direction of the Poynting vector is perpendicular to both the electric field (E) and magnetic field (H) vectors.
  • Poynting vector unit is W/m².
  • Poynting theorem states that the net power flowing out of a volume is equal to the rate of decrease of stored electromagnetic energy minus conduction losses.

Complex Form of the Poynting Vector

  • The complex Poynting vector (S) is represented as S = E × H*
  • E and H are phasors of time harmonic fields.
  • S has a dimension of watts/m².
  • S is related to the time-averaged Poynting vector by S(r,t) = Re{S(r,w)}.
  • The divergence of the complex Poynting vector is given by ∇·(E×H*) = -jω(μH² - εE²)-J*E.
  • This formula shows the relationship between the complex Poynting vector, the stored energy, and the power dissipation in a given volume.

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Description

Explore the concepts of the Poynting vector and theorem in electromagnetic waves. Learn about the mathematical representation, the direction of energy flow, and the complex form of the Poynting vector. This quiz will test your understanding of energy density, flow, and the relationships between electric and magnetic fields.

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